It is known in the art to achieve a fine small increment adjustment of a seat recliner employing toothed sector and pawl locking means by a differential translation drive of the toothed sector involving mechanical disadvantage resulting in multiplied arcuate movement of the toothed sector for a given angular movement of the backrest. Examples of patents disclosing such mechanism are British Pat. No. 1,325,509 and U.S. Pat. No. 3,902,757. However, such prior adjustable hinge constructions involve the requirement for releasing the adjustment mechanism to accommodate forward tilting of the backrest and consequently readjustment to a desired angular position of the backrest following each passenger exit and entrance to the rear seat of a two-door passenger car.
Inertia latches are also known to accommodate forward tilting of a backrest without requirement for manual latch release when the vehicle is stationary while blocking such forward tilting under conditions of severe braking or impact from front end collision. Examples of such inertia devices are U.S. Pat. Nos. 2,873,794, 3,433,524 and 3,628,831. However, such patents do not teach the problem or solution for adapting such an inertia latch mechanism to an adjustable recliner seat where the seat angle presents a varying condition for gravity relationships relative to inertia moment arms.
The closest known prior art is a commercially produced construction wherein only a coarse adjustment of sector teeth resulting from direct equal angular displacement with the backrest has the feature of an inertia latch release. Such a hinge fitting has been employed by the Ford Motor Company on certain of its models as an optional feature sold under the "Superlatch" trade name.